The present invention relates to a boot for protecting a universal joint or the like mounted on a connecting portion of a propeller shaft, for example, from rain water, mud, etc., and particularly to a boot capable of preventing leakage of grease sealed into the boot.
For example, in a power transmission apparatus for transmitting the drive of an engine of an automobile to driving wheels, a universal joint such as an constant velocity joint is used. Dust boots are provided to protect the joint from rain water, mud, etc.
A conventional construction of a connecting portion between a drive shaft and a wheel is as shown in FIG. 4.
First, an constant velocity joint 20 includes an outer ring 21, an inner ring 22 and a ball 23. The outer ring 21 is secured to a wheel (not shown), whereas the inner ring 22 is secured to a drive shaft 24.
Further, the ball 23 is interposed between the outer ring 21 and the inner ring 22 whereby the driving force of the drive shaft 24 can be transmitted to the wheel while uniformly maintaining the number of revolutions of the drive shaft 24 and following the steering and up- and downward movement of the wheel.
A boot 25 formed of rubber or resin is mounted between the drive shaft 24 and the outer ring 21 in order to protect the outer ring 21, the inner ring 22, and the ball 23 constituting the constant velocity joint 20 from rain water, mud, etc.
The conventional boot 25 has anaxially expansible bellows portion 26, opposite ends of which are formed with openings 27 and 28, fixed portions 29 and 30 being formed to secure the boot to the outer ring 21 of the constant velocity joint 20 and the drive shaft 24.
The boot 25 is mounted to the outer ring 21 and the drive shaft 24 while spreading on the fixed portions 29 and 30, and finally a clamp 31 is fastened to thereby secure the boot 25 to the outer ring 21 of the constant velocity joint and the drive shaft 24.
Since grease supplied to the sliding portion of the constant velocity joint is sealed into the boot, it is necessary to secure the sealing property between the inner surfaces of the fixed portions, and the outer ring and the drive shaft.
In the past, as the construction for improving the sealing property of the kind as described, there has been proposed an arrangement wherein, as shown in FIG. 5A, annular projections 32 are formed on the inner surfaces of the fixed portions 29 and 30, and the projections 32 are crushed by the compressive force when the clamp 31 is fastened.
However, the projections 32 heretofore proposed had the construction that the projections were compressed verticaly relative to the contact surface making use of the fastening force of the clamp. The fastening force of the clamp or band is shown by the downward arrow in FIG. 5B. Therefore, the distribution of the surface pressure acting on the shaft 24 from the projections 32 was uniform in the axial direction as shown in FIG. 5B. If the fixed portion 30 of the boot is deviated toward the inside of the boot, the distribution of the surface pressure acting on the shaft 24 from the projections 32 varies so that the surface pressure of the inside of the boot lowers. For this reason, the grease sealed into the boot was likely to leak.